Networks are shifting from current circuit switching networks to packet exchange networks, and Next Generation Network (NGN) representing such shift has been established. The NGN is configured to implement voice communication using the network while maintaining voice communication quality equivalent to the quality of the current circuit switching networks and so on.
Thus, it is more important to estimate voice communication quality in a next generation network represented by the NGN, and measurement technology for evaluating voice communication quality on a middle path and a terminal of the network is required. That is, technology for testing voice quality degradation used for estimating the voice communication quality from data being transferred is necessary. In particular, technology for analyzing data during operation, i.e., so called active measurement technology is required.
Japanese Laid-open Patent Publication No. 2000-332758 and Japanese Laid-open Patent Publication No. 07-250107 disclose technology for estimating voice quality.